Take energy. Today, 70 percent of it comes from fossil fuels, a 19th-century technology. But if we could capture just 1/10,000th of the sunlight that falls on Earth, we could meet 100 percent of the world's energy needs using this renewable and environmentally friendly source. We can't do that now because solar panels rely on old technology, making them expensive, inefficient, heavy, and hard to install. But a new generation of panels based on nanotechnology is starting to overcome these obstacles. The tipping point at which energy from solar panels will actually be less expensive than fossil fuels is only a few years away. The power we are generating from solar is doubling every two years; at that rate, it will be able to meet all energy needs within 20 years.